Locking device more particularly for connection between a barge and a pusher tug

ABSTRACT

A locking device more particularly for the connection between a barge and tug comprises an interrupted screw and nut assembly.

United States Patent 1191 Colin Jan. 29, 1974 22 Filed:

[ 1 LOCKING DEVICE MORE PARTICULARLY FOR CONNECTION BETWEEN A BARGE ANDA PUSHER TUG [75] Inventor: Jean Paul Colin, Nantes, France [73]Assignee: Societe Financiere Et Industrielle Des Ateliers Et ChantiersDe Bretagne, Nantes, Loire Atlantique, France Feb. 10, 1972 211 Appl.No.: 225,237

[30] Foreign Application Priority Data Aug. 31, 1971 France 7132331 [52]U.S. Cl 114/235 A [51] Int. Cl B63b 21/60 [58] Field of Search 114/235A, 235 R; 188/67; 92/15, 23; 85/32 V, 1 L, 1 R; 287/103 A PrimaryExaminer-George E. A. Halvosa Assistant ExaminerPaul .E. SaubererAttorney, Agent, or F irm-Stevens, DaVisfM iller & Mosher [57] 'mABSTRACT A locking device more particularly for the connection between abarge and tug comprises an interrupted screw and nut assembly. a

7 Claims, 7 Drawing Figures LOCKING DEVICE MORE PARTICULARLY FORCONNECTION BETWEEN A BARGE AND A PUSIIER TUG This invention relates to alocking arrangement primarily for use in connecting devices betweenseagoing barges and pusher tugs.

Of course, seagoing barge/pusher tug combinations need specialconnection facilities between the barge and the tug because of theextreme forces which the connection must be able to withstand in verybad weather conditions. For instance, the tug bows can have inclinedsurfaces engageable between corresponding surfaces at the barge stern bythe thrust of the tug screws, after the fashion of a pyramidal wedgeengaging in a pyramidal recess. To ensure that the connection is verystrong at the end of the engaging movement, a clamping force is providedby a very powerful hydraulic ram or the like whose casing is rigidlysecured to the tug while the rod of the ram or actuator is rigidlysecured to the barge. The clamping force must be maintained throughoutthe voyage. At the end of the voyage the tug is disconnected from thebarge,- an operation in which more force is required than for clampingbecause of the jamming effects (which depend upon the inclination of thesurfaces and upon the coefficient of friction of the metal sheeting).The actuator is responsible for providing the forces for disengagement.

The clamping force must be maintained through the voyage, moreparticularly in bad weather, and must not be affected by any failure ofthe hydraulic station. Consequently, the actuator rod must be lockedmechanically upon completion of the operation of connecting the barge tothe tug.

It is an object of this invention to provide mechanical means for thislocking. It is another object of this invention to provide means whichprovide as high a safety factor as is provided by the pressurisedactuator and which can also produce locking in the exact instantaneousposition of the actuator rod at the time when the latter means areoperated. The last-mentioned position is never exactly the same, varyingat each engagement operation because of slight variations of the maximumpressure in the actuator cylinder, because the tug never presents inexactly the same position to the barge and, more particularly, becausethe barge to which any given tug is connected is always different fromthe previous barge. The resulting variations are not more than from 0.1to 0.2 metre. Upon the completion of hydraulic actuation the mechanicallocking is operated and the ram or actuator ceases to be energised,whereafter forces are transmitted by the mechanical locking facilityalone.

In the drawings:

FIG. 1 is an overall view of the apparatus;

FIG. 2 is a section through the locking mechanism according to thisinvention;

FIGS. 3-5 are developed partial views showing the meshing of thescrewthreads of the locking device; and

FIGS. 6-7 are diagrammatic views of means for obviating jamming of thecooperating members.

Referring to F IG. 1, a ram or actuator casing l terminates in anarticulated yoke 3 which transmits forces to a pusher tug. A system 4providing a connection to the barge (hook or yoke or any other system)is disposed at the end of actuator rod 2. The same is retractedsubstantially completely in the navigation position. The

rod 2 needs to be locked in this position, which is never the same butwhich, as just stated, varies by not more than about 0.1 meter from itsaverage position.

Rod 2 is extended by a widened or thickened part 5 which merges into thebarge connection system 4. Since the rod 2 is retracted substantiallycompletely after locking, part 5 is near the end of the actuator casing.Part 5 is machined like the male element of an interrupted-thread typescrew-and-nut system. Of course, this kind of locking, which is currentin artillery breeches, comprises a nut-and-screw system in which each ofthe metal members is reduced to the thread troughs over n cylindricalbands bounded by cylinder generatrices of angular opening 21r/2n, withtwo consecutive smooth bands i.e., flattened screwthreads beingseparated from one another by a band which has the same angular opening21r/2n, but in which the screwthreads are retained. When the plainsectors of one member are presented to the screwthreadeds'ectors of theother member, the screw is slid into the nut, whereafter the respectivescrewthreadings are engaged with one another by a rotation through21r/2n.

Rod 2 extends through a nut 6 which is formed with interruptedscrewthreads so as to cooperate with the screwthreading of part 5. Nut 6can rotate around itself but is axially connected to the actuator casingby very rugged abutments. Nut 6 is placed at such a distance from theactuator casing that upon the completion of clamping i.e., when the rod2 is virtually completely retracted the screwthreaded portion of part5extends completely through nut 6, the length of part 5 being greaterthan the thickness of the nut 6 by a little more than 0.2 m to allow forthe uncertainty of the endof-clamping position.

At the time at which the tug engages with the barge, the nut 6 is in aposition such that the screwthreads are disengaged. Actuator rod 2 ispushed fully out. End 4 is connected to the barge. Pressure is appliedto the opposite surface of the actuator piston and the rod moves back,connecting the tug tothe barge, as far as the locking position. Achangeover should then be made from hydraulic locking to mechanicallocking by turning the nut and fully engaging the respectivescrewthreads.

Unfortunately, in most cases when the nut is rotated the spaces andlands of the screwthreaded parts of the 'screw and nut are not oppositeone another and the screw and nut cannot be turned through 21r/2nrevolutions to produce locking. The nut must be moved slightly until thenut and screw coincide and the nut can be rotated.

According to the invention, to achieve such movement the nut 6 (FIG. 2)has around it an outer concentric ring 7. The nut 6 and ring 7 have acommon plane bearing surface 8. After entering into screwthreadedengagement with the rod and with effect from the time when the actuatorceases to be pressurised, the nut tends to be moved away from theactuator casing by the forces tending to separate the two vessels.Surface 8 transmits these forces to the ring 7, which transmits them tothe actuator casing. Accordingly, ring 7 has peripheral screwthreading 9to the same hand and of the same pitch as the interrupted screwthreadingof nut 6. screwthreading 9 is engaged in a tapping of a sleeve 10rigidly secured to actuator casing 1. I v

The nut rotates solidly with the ring through the agency of means whichkeep the bearing surfaces of the nut and ring clamped fairly tightlytogether to an extent sufficient to produce a friction force developinga limited drive torque. By way of non-[imitative example, one way ofproducing a clamping of this kind is by means of a number of cylindricaltappets 11 which are received in blind apertures in ring 7 and which arebiased by strong compression springs 12, the tappet heads bearing on arim 13 rigidly secured to nut 6.

Ring 7 is rigidly secured to a concentric toothed disc 14 meshing with astraight-toothed pinion 15 driven by a motor 16.

Once maximum hydraulic clamping has been achieved, motor 16 is startedso as to screw the moving members tighter. The ring is therefore screwedinto sleeve 10. However, the nut, which tends to turn because offriction between the bearing surfaces, cannot rotate since the profilesof the interrupted screwthreads do not coincide with one another. Thenut therefore just moves rectilinearly and parallel to the axis of theactuator rod, the bearing surfaces 8 remaining in contact.

Once the profiles coincide with one another, the nut can rotate and itsscrewthreads engage in the screwthreads of the actuator rod. Themovement continues until full engagement i.e., for a rotation of 21r/2nwhereupon an abutment 17 stops rotation of the nut. The motor, as itcontinues to rotate, tends to force the ring into the sleeve andtherefore to clamp the ring against the nut on the bearing surface.After a short take-up movement, the system is stopped by the motorseizing, unless a force limiter is provided between the motor and thepinion 15.

As a non-limitative example the abutment 17 .can be a finger which isrigidly secured to the actuator casing and which is engaged in acircular slot 18 extending over a sector of not more than 21r/2n plusthe diameter of the finger 17. When the same abuts one end of the slotthe screwthreads are fully released; when the finger abuts the other endof the slot the screwthreads are fully engaged.

For mechanical release, the actuator is pressurised enough to cancel theload operative on the sleeve and actuator rod screwthreads and the motoris run to the opposite hand. In practice the motor is run, and then thepressure applied to the actuator is increased. Once the screwthreads arefree enough the nut 6 rotates and releases the actuator rod.

Motor 16 can be hydraulic or pneumatic or electric. Preferably, it is ahydraulic motor with a maximum torque such that there is no risk ofbreaking the tooth systems of the wheel 14 and pinion 15 when the latteris immobilised at the end of the locking operation. No force limiter istherefore needed. The slow rotation and high torque make a hydraulicmotor very suitable for this purpose.

The motor control should have an interlock facility to obviate any riskof the following occurring.

When the interrupted-thread nut-and-screw system is machined, twoclearances are left. The first clearance is left between the male andfemale screwthreads to preclude any risk of seize-up in tightening(clearance between screwthreads). The second clearance or backlash isoperative between the cross-cut and non-crosscut portions of the threadsand enables the screw to slide properly in the nut without any risk ofaccidental jamming between cross-cut ends of the screwthreads (slidingclearance).

When the motor is started the nut first makes a slight helical movementcorresponding to about half of the sliding clearance. As a rule, theedges of the nut screwthreads then abut the edges of the screw, thescrewthreads not being in coincidence. The nut then starts to slidelongitudinally as mentioned previously.

However, the opposite case may occur occasionally i.e., with thescrewthreads in a coincidence position the screw may continue itshelical movement until full engagement. FIGS. 3-5 relate to the lattercase; they are developed views in a plane of a part of the screwand-nutassembly through a coaxial cylinder extending half-way along the heightof the screwthreads at the time at which the motor starts. Hatchedsurfaces 25 represent the screw screwthread sections and hatchedsurfaces 26 represent the nut screwthread sections. The blocking forceis transmitted via flanks 27, 28; after locking, flanks 29, 30 areseparated by the full thread clearance.

The case of maximum coincidence between the profiles is shown in FIG. 3,with the thread clearance distributed equally between all the flanks ofthe thread. FIG. 4 shows the extreme case in which the distance betweenthe flanks 27 and 28'is equal to the thread clearance. The flanks 29, 30are in extension of one another. If there is actual mechanical contactthere will be a very slight sliding movement before screwing begins.

In the other extreme case, shown in FIG. 5, flank 28 is in extension offlank 27. Either a screwing or a sliding movement occurs according asflank 27 is slightly to one side or the other of this ideal position.Very near this position there is a very narrow zone in which theperpendicular to the bearing surfaces makes an angle less than the angleof friction with the screwing direction. In this zone jamming occurs,the motor jams and the connection cannot be screwed up. The profiles maycoincide rarely in this way and jamming is even more exceptional;however, jamming must be obviated since it prevents mechanical lockingof the actuator.

According to the invention, to obviate this risk an indicator of screwlongitudinal position moves past a scale on the nut. A zone, e. g.,about a quarter of a pitch long, is defined in which the jammingposition is e.g., at the centre. Starting of the motor for mechanicallocking is inhibited when the indicator is in such zone.

In practice, a sensor can continuously check the indicator. When theoperator operates the locking contactor, the motor can start in thescrewing direction subject to the detector finding the indicator to beout of the forbidden or inhibited zone. If this is not the case,operation of the locking contactor starts the motor to the opposite hand(unscrewing). The nut slides away from the actuator casing until thedetector detects the indicator as having left the forbidden zone,whereupon the motor stops, then starts in the required direction(screwing), and the interlock is cut out of circuit until the end oflocking (since it would operate again as the nut approached the screwingposition). The indicator position detector can be a contactor which ismounted on the nut and whose sensing element rests on the screw tooth.Alternatively, the detector can be a magnetic proximity detector borneby the nut, a signal being triggered by the presence of the crest of ascrew screwthread.

FIG. 6 shows a circuit diagram for a device of this kind comprising: atough contactor or a proximity detector D having a contact d d atransient-make relay A having a normally open contact set a which whenenergised closes for a fraction of a second long enough to attract thearrnatures of another relay then remains open until subsequentenergisation; a relay B whose opening is delayed for a brief fraction ofa second, e.g. 0.2 second, and which had contacts b b and b b and aconventional relay C.

Relay C comprises changeover contacts C C C and contacts C C With therelay off the contacts C C make, and if current is applied via C thecontactor or solenoid valve controlling motor 16 starts the same in thescrewing direction. When relay C is energised its contacts C and C maketo start motor 16 running in the unscrewing direction.

For locking, a maincontactor 20 is closed to energise the system. Thebrief closure of contacts a,, a of relay A energises relay B which doesnot drop immediately because of its delay feature.

If the respective screwthreads are positioned relatively to one anotherin the dangerous zone with jamming at the centre, detector D closescontacts d d and, via contacts b 12 (B having picked up), relay C picksup and provides a make via its contacts C C the motor starting to run inthe unscrewing direction.

Relay C also closes its contacts C C to enable relay B to stick via theclosed contacts b b of relay B.

Once the screwthreads have moved away from the dangerous position, thedetector opens contacts d d so that the relay C drops. The motor stopsand starts to run in the screwing direction. Since relay C is notenergised, the contacts C and C open so that, after a very brief delay,relay B drops and opens contacts b b and b;,, b.,. During the screwingmovement the screwthreads return to the dangerous zone, whereupon thedetector closes contacts d d however, since the circuit is not made, thecontacts b b. being open, relay C stays of and screwing is completed.

The reason for the very brief delay feature of relay B is that thelatter causes relay C to pick up, which provides the stick feature forrelay B. There would therefore be a risk of B dropping before the stickis established.

Actually, the motor starts immediately the danger zone is entered, thenruns in the opposite direction, so that it re-enters the danger zone;however, because of the inertia of the moving parts and because of thedifferential of the detector, there is left between detection of entryand detection of exit an appreciable time in which relay B has plenty oftime to open despite its brief delay feature.

The invention provides other ways and means of obviating a risk ofjamming.

If jamming occurs it causes the motor to seize up almost immediately atstarting. This virtually immediate stoppage is detected by a delay logicwhich immediately starts the motor in the opposite direction for a timewhich depends upon one another delay feature and which is roughly equalto the time taken for the nut to move, e.g., over a distancecorresponding to half of one pitch. Upon completion of this reverserunning the motor starts to run in the screwing direction until thecompletion of locking.

F lG. 7 is a corresponding diagram. This suggestion is of use only inthe case in which screwing is performed by an electric motor, sincejamming can be detected by the appearance of overcurrent in the line ofthe jammed motor. The equivalent pressure peak is much less marked inthe case of a hydraulic motor and might be inadequate for detection.

The equipment comprises:

A relay E which acts as detector and which is connected in the motorline and which has a normally open contact set e e a transient-makerelay F which has a contact set f f a first relay G whose opening isdelayed for slightly longer than the time which the nut takes to turnthrough an angle equal to the sliding clearance (as an example, an angleof 360/20n, knowing that the screw and the nut each have n screwthreadedsectors separated by n plain intervals), the relay G having a contactSet 1 gt;

a second relay H whose opening is delayed for a time corresponding tothe time taken by the nut to turn through an angle equal to 25 percentof the pitch, relay H having a contact set h h and a conventional relayJ whose outputs J J J as in the previous example, control the startingof the motor in the screwing or unscrewing direction.

For locking, contactor 20'is closed. Relay F causes relay G to pick up.The main relay J, which is not energised, starts the motor in thescrewing direction.

If jamming occurs, the time when it occurs is the time at which thelateral sliding clearance between the screw and the nut has been takenup. The delayed relay G has therefore not yet dropped. The current relayE responds to the overload caused by the jamming by closing its contactse e Relay H therefore picks up by contacts g g and e e and its contactsh I1 therefore close. Relay J picks up, its contacts J J make and themotor first stops, then starts to run in the unscrewing direction.

Upon disappearance of the overcurrent, detector E opens its contacts e ehowever, energisation of relay H is interrupted at the contacts h,, h bythe delayed relay F dropping either slightly before or slightly afterthe opening of the contacts e e The now deenergised relay H drops aftera time in which the nut has moved about 25 percent of a pitch relativelyto the screw. The relay J, since it is not energised, drops in turn. Themotor stops, then restarts in the screwing direction and runs until thecompletion of locking, since the end-of-locking overcurrent detected bythe relay E has no effect, the contacts g g being open. This overcurrentcuts out an interlock relay (not shown) on the general control panel;such relay should be adjusted to react more slowly than the detector E.

I claim:

1. A locking device for connecting a barge and a pusher tug, comprising:two elements adapted to slide longitudinally relatively to one another;a screw on one element and a nut on the other element engaged on saidscrew, the screwthreads of the screw and of the nut being interrupted inlongitudinal bands which are the same width as one another, andseparated in pairs by bands of screwthreads of the same width as theinterrupting bands; a screwthreaded ring screwed into a tapped bearingsurface of the nut-bearing other element, such bearing surface being onthe same axis, in the same direction and of the same pitch as thescrewthreading of the nut; friction means between the ring and the nutfor rotating the nut via the ring; drive means for rotating the ringaround its axis, and abutment means to limit the rotation of the nutbetween one position in which the interrupted screwthreads of the screwand nut are fully engaged and another position in which the interruptedscrewthreads of the screw and nut are fully disengaged.

2. The device of claim 1 wherein the drive means comprise a forcelimiter,

3. The device of claim 1, also comprising: a detector for checking onthe relative position of the nut and screw; means for temporarilyreversing the direction of drive means rotation when the detector findsthat the nut is near a jamming position on the screw at the start of thelocking operation and for cancelling such reversal after the screw hasshifted relatively to the nut by a fraction of the pitch so that the nutresumes rotation in the screwing direction; and means for cutting thedetector out of circuit until the subsequent locking operation.

4. The device of claim 3 wherein the temporarily operating meanscomprise a transient-make relay which is controlled by the detector andwhich controls a delayed relay, the latter in turn controlling areversing 8 relay which is connected in the drive means control circuitand which is responsible for the sticking of the delayed relay.

5. The device of claim 1 wherein means are provided to detect stoppageof the drive means after the starting thereof and to temporarily reversethe direction of drive means rotation so as to move the nut back by afraction of the pitch, whereafter the nut resumes its rotation in thescrewing direction, to prevent jamming of the nut on the screw.

6 The device of claim 5 wherein the means comprise a short-durationcontact relay controlling a first delayed relay, one contact of which isin series with one contact of a drive means stoppage detector andcontrols a second delayed relay which controls a reverser connected inthe drive means circuit.

7. The device of claim 6 wherein the drive means comprise an electricmotor and the stoppage detector is a current detector.

1. A locking device for connecting a barge and a pusher tug, comprising:two elements adapted to slide longitudinally relatively to one another;a screw on one element and a nut on the other element engaged on saidscrew, the screwthreads of the screw and of the nut being interrupted inlongitudinal bands which are the same width as one another, andseparated in pairs by bands of screwthreads of the same width as theinterrupting bands; a screwthreaded ring screwed into a tapped bearingsurface of the nut-bearing other element, such bearing surface being onthe same axis, in the same direction and of the same pitch as thescrewthreading of the nut; friction means between the ring and the nutfor rotating the nut via the ring; drive means for rotating the ringaround its axis, and abutment means to limit the rotation of the nutbetween one position in which the interrupted screwthreads of the screwand nut are fully engaged and another position in which the interruptedscrewthreads of the screw and nut are fully disengaged.
 2. The device ofclaim 1 wherein the drive means comprise a force limiter.
 3. The deviceof claim 1, also comprising: a detector for checking on the relativeposition of the nut and screw; means for temporarily reversing thedirection of drive means rotation when the detector finds that the nutis near a jamming position on the screw at the start of the lockingoperation and for cancelling such reversal after the screw has shiftedrelatively to the nut by a fraction of the pitch so that the nut resumesrotation in the screwing direction; and means for cutting the detectorout of circuit until the subsequent locking operation.
 4. The device ofclaim 3 wherein the temporarily operating means comprise atransient-make relay which is controlled by the detector and whichcontrols a delayed relay, the latter in turn controlling a reversingrelay which is connected in the drive means control circuit and which isresponsible for the sticking of the delayed relay.
 5. The device ofclaim 1 wherein means are provided to detect stoppage of the drive meansafter the starting thereof and to temporarily reverse the direction ofdrive means rotation so as to move the nut back by a fraction of thepitch, whereafter the nut resumes its rotation in the screwingdirection, to prevent jamming of the nut on the screw.
 6. The device ofclaim 5 wherein the means comprise a short-duration contact relaycontrolling a first delayed relay, one contact of which is in serieswith one contact of a drive means stoppage detector and controls asecond delayed relay which controls a reverser connected in the drivemeans circuit.
 7. The device of claim 6 wherein the drive means comprisean electric motor and the stoppage detector is a cuRrent detector.